Abstract

Two multicharacter clines in the more or less continuous stands of Eucalyptus gunnii-archeri on the Central Plateau, Tasmania, are genetically based and appear to parallel independent habitat gradients. Results from experimental gardens established near the extremes of each cline suggest that these clines are at least partly maintained by spatially varying selective forces. Spatial variation in population fitness could be partly attributed to a differential response to drought, frost and insect predation.
Most characters associated with extension growth (e.g. height, internode length, leaf size) exhibited marked phenotypic plasticity. In contrast, several characters of taxonomic importance in the complex, and which vary markedly between populations (e.g. seedling leaf shape, glaucousness), exhibited little environmental modification. The ontogenetic pattern varied between populations and, for many charac- ters, the direction of environmental modification was the same as the direction of genetic differentiation.